Scientific Method —

Hacking the FUSE in space

As parts of the Far Ultraviolet Spectroscopic Explorer space observatory have …

Although the Hubble space telescope gets much of the press, NASA has a number of orbiting observatories. And, just like the Hubble, these have parts that fail and could use replacement. Most of them, however, don't have the orbit, cost, or profile to allow a repair mission. Such was the case with the Far Ultraviolet Spectroscopic Explorer, or FUSE. Launched in 1999, the orbiting observatory relied on four reaction wheels (3 main and a backup) to maintain its orientation in space. Unfortunately, two died in 2001, potentially bringing a rapid end to the scientific mission.

Unable to repair it, NASA engineers essentially scavenged the observatory itself for spare parts. What they came up with were Magnetic Torque Bars. These controllable electromagnets have been drafted to reorient the satellite by twisting it against earth's magnetic field. Combined with the remaining two reaction wheels, this allowed for several more years of successful observations. A third reaction wheel failed last year, but after 10 months of fine tuning the control program, observations started up again in November, using the torque bars to handle two of its axes of motion. For more on this and the discoveries made by FUSE, you can check out its press release web page.